There are many applications for wide angle imaging systems, including “fish eye” lenses or other distorted view imaging systems. For example, wide angle imaging has many applications in security and surveillance, such as close circuit surveillance of property or other monitoring.
When the video camera is used with a conventional fish eye lens, e.g., one with a field of view of 180 degrees, the image output by the camera (and projected onto an electronic imaging device) is distorted, usually circular. The field of view of a camera with a fish eye lens is illustrated in FIG. 1.
FIG. 1 shows a camera 100 with wide angle lens system (such as a 180 degrees fisheye lens). Camera 100 view is broken down into two types of region, including main areas of interest 102 and central region 104. Because of the distortion introduced by the wide angle lens system of camera 100, the main areas of interest 102 are typically warped and occupy the periphery of any optical image output by camera 100. This distortion is typically circular for a circular imaging system, but can be of other shapes, depending on the lens system implemented.
Cameras such as that depicted in FIG. 1 often output an optical signal which is projected or otherwise input to an electronic sensor, such as (but not limited to) a charge-coupled display (hereinafter “CCD”) or complementary metal-oxide semiconductor (hereinafter “CMOS”) sensor system. Sensors used in a video camera are generally rectangular, so part of the sensor's photo-sensitive area is wasted since it is not illuminated by the circular image projected onto its surface. Alternatively, depending on the projection scheme used, the optical signal may be projected so as to cover most or all of the sensor area, but this results in lost information from the optical signal. These cases are illustrated in FIGS. 2A and 2B.
FIG. 2A shows a system wherein an optical signal is projected onto an image sensor. In this example, most of the area of the sensor 200 is occupied by the lens image circle 202 (though some of the image sensor 200 is not occupied and is thus wasted sensor region 208). In this example, in order to maximize the main region of interest 204 on the sensor 200, some of the lens image 202 is lost, as depicted by lost image region 210. Central region 206 is also shown, and typically comprises the least distorted region of the output optical signal. Main region of interest 204 typically includes more distortion, depending on the lens system used to gather the image.
FIG. 2B shows another situation, wherein the entire lens image circle 202 is projected within the boundaries of image sensor 200. This situation results in a greater wasted sensor region 208 and also requires the region of interest 204 and central region 206 to occupy a smaller area of the sensor 200, meaning the optical image covers fewer detectors or pixels, and thus has lower resolution.
Often, the peripheral region of the field of view is the desired area for surveillance applications that require visibility of a panorama. This corresponds, for example, with regions of interest 204. Because the region of interest may be on the periphery of the total captured image, and because the image was captured with a lens system that introduces greater distortion on the periphery (such as the case with a fisheye lens system or other wide-angle lens system), the region of interest may include high amounts of distortion while covering a relatively small area of the available image sensor region. This results in an inefficient use of the sensor region, lower resolution in the areas of interest, and higher resolution in areas that are of lower interest.
Wide Angle Electronic Camera with Improved Peripheral Vision
The present invention, in one example embodiment, provides a system and method for improving the peripheral imaging of a distorted optical image.
For example, one embodiment relates to the design of a video or still camera with a novel optical system and an electronic image processing system. The optical system captures the image and distorts it such that regions of interest are expanded as they are projected onto a sensor. The electronic image processor then eliminates the distortion by applying a substantially opposite distortion compared with the distortion introduced by some or all of the optical system.
In preferred embodiments, the present innovations are applied to increase resolution of regions of interest, and/or to improve the fit of a non-rectangular image to a rectangular image sensor, for example. Of course, these innovations, as described below, can be used in other shaped optical and sensor implementations.
The increase in resolution provides capability to magnify (by increasing resolution of) one or more regions of interest, while trading off resolution in one or more regions outside the region(s) of interest.
The disclosed innovations, in various embodiments, provide one or more of at least the following advantages:                improved resolution in regions of interest;        magnification capability for regions of interest beyond normal magnification capability;        more efficient use of sensor area;        capture of all or a greater percentage of a whole image while improving resolution in a specific region or regions.        